The present invention relates to a nonwoven fabric wiper used to wipe stains off from an object to be cleaned and a method for making it.
U.S. Pat. No. 3,616,175 discloses a method for a nonwoven fabric for wipers wherein high pressure water is jetted onto a web of rayon fibers placed on a wire mesh from nozzles with fine orifices arranged above the web to entangle the fibers and thereby to obtain the nonwoven fabric wipers. Japanese Patent Application Publication No. 1985-11148, on the other hand, discloses a method for making a nonwoven fabric for wipers wherein a web of thermoplastic polymer filaments is laminated with a mat of thermoplastic polymer microfibers and these components of the laminate are bonded together by intermittently heating them under a pressure to obtain the nonwoven fabric which is excellent in the surface friction characteristic. According to the first-mentioned method, the wire mesh leaves its pattern on the surface of the finished nonwoven fabric which has been in contact with the wire mesh and the high pressure water jets form recesses on the other surface of the finished nonwoven fabric so that the mesh pattern and the recesses form together relatively fine undulations on the respective surfaces. The fibers are mechanically entangled and the nonwoven fabric is generally soft to the touch. In the nonwoven fabric obtained by the second-mentioned method, the spots intermittently heated under a pressure are heat sealed and thinned relative to the remainder so as to form relatively noticeable undulations on the surfaces which well contribute to scrape stains off from an object to be cleaned.
Of the products obtained by the above-mentioned prior art, the nonwoven fabric formed by entangling the fibers under the effect of high pressure water certainly has the undulations on the surfaces, but these undulations are too fine and soft to achieve the desired function of scraping stains off from an object to be cleaned. On the other hand, the nonwoven fabric obtained by partially or intermittently heating the thermoplastic polymer under a pressure is effective to scrape stains off from an object to be cleaned, since the tissue of each heat sealed spot is appropriately rigid and the undulations are relatively noticeable. However, the heat sealed spots lose a fibrous configuration and is solidified, making it difficult to achieve a desired soft touch.
Accordingly, it is a principal object of the invention to overcome the above-mentioned problems of prior art by jetting high pressure water onto a fibrous web containing therein thermally shrinkable fibers to form a nonwoven fabric of uneven fiber distribution density which is then heated to crimp the thermally shrinkable fibers and thereby surface-finishing a wiper with relatively noticeable undulations.